There is a piezoelectric type electroacoustic transducer known as an electroacoustic transducer used for a mobile apparatus or the like. The piezoelectric type electroacoustic transducer generates oscillation amplitude using expansion and contraction motion which is created when an electric field is applied to a piezoelectric vibrator. As a technology which relates to the piezoelectric type electroacoustic transducer, for example, there is a technology which is disclosed in Patent Document 1. This technology is used to connect a pedestal, which is used to paste up a piezoelectric element, to a support member through a vibrating membrane which has lower rigidity than the pedestal.
The piezoelectric vibrator is used for, for example, a superdirective speaker using ultrasonic wave. As a technology which relates to the superdirective speaker, for example, there are technologies disclosed in Patent Documents 2 to 5. The technology disclosed in Patent Document 2 is used to form an audible sound field at an arbitrary point in a space by controlling the phase of ultrasonic wave. The technology disclosed in Patent Document 3 is used to output ultrasonic wave in two directions, that is, a surface side and a rear surface side. The technology disclosed in Patent Document 4 relates to a superdirective speaker which combines an ultrasonic wave speaker with a wide area speaker. The technology disclosed in Patent Document 5 relates to a post for a man conveyor which includes a superdirective speaker that outputs ultrasonic wave, and a filter which attenuates the ultrasonic wave area of audible sound.